The present invention relates to a spinning preparation process and device with a mixer for mixing fibres and with a withdrawal device for withdrawing the fibres from the mixer, and a separating device for separating foreign matter from the fibres.
The spinning preparation device in accordance with the invention is mainly used in blowroom lines for the preparation of cotton in order to prepare the same for spinning. Blowroom lines consist substantially of a bale opener which opens the supplied raw cotton, which is then further conveyed in the form of flocks. In this process, coarse impurifications of the cotton are separated. Usually, the fibre flocks then come into a mixer which ensures a thorough mixing of the fibre flocks by way of various chutes, for example. The fibres are then taken from the mixer by means of an elevator lattice and are conveyed further on.
From DE 195 16 568 it is known to arrange a separating device downstream of a bale take-off machine or a mixer, which separating device is used for separating foreign matter from the fibres. In this separating device, the fibre flocks are conveyed by way of a pneumatic conveyance from the preceding machine, such as a mixer, to a filling chute from where they are taken out by way of an opening device. The opening device consists of a slowly revolving draw-in roller and an associated opening roller, for example. The fibres taken by the opening device from the filling chute fall into a chute-like chamber which is part of a separating device for separating foreign matter from the fibres. For this purpose, the opened fibre flocks move past an optical sensor system in free fall in the form of a kind of fibre fleece.
The cotton opened into fibre flocks not only contains natural impurifications such as dust or trash particles, but also foreign matter such as fabric made of jute or cotton, strings, webs or plastics of all kinds as well as fibre flocks which are soiled with oil to such an extent that their further presence would considerably impair the further processing of the cotton. These impurifications are recognized in the known apparatus by means of optical colour sensors and removed from the free-falling stream of flocks by way of a controlled blow-out device.
From DE 44 30 332 A1 a separating device for separating foreign matter is known in which fibre flocks pneumatically supplied in a conveying chute are condensed. The fibres are conveyed past a wall for the optical recognition of foreign matter by means of a conveyor belt. As a result of the wall, such as a glass plate, for example, and the conveyor belt, the fibre flocks are formed into a fleece and conveyed in this form past the optical sensors of the separating apparatus by the conveyor belt. The optical sensors are arranged at the glass wall and can thus recognize the imperfections.
The known spinning preparation devices with a separating device for separating foreign matter have the disadvantage that the fibre flocks, before they reach the separating device, have to be subjected to a renewed treatment after having been pneumatically conveyed. This is necessary in order to prepare them in such a way that they can be supplied to the separating devices in the required form in order to recognize the foreign matter. For this purpose they are re-condensed and then opened into flocks again, or taken from a conveying chute and formed into a fibre fleece. A condension of the fibres is also made, for example, when the fibres are conveyed from the spinning preparation device to the separating device by means of pneumatic lines, which means the separation of conveying air. For the recognition of foreign matter, it is advantageous, however, if the fibres are present in the thinnest possible fibre or flocked fleece so that the foreign matter cannot be covered by batch fibres and thus cannot be recognized. These renewed treatments require considerable efforts both in construction and lead to high energy (and air) consumption.